A dual reaction-mass dynamic vibration absorber for active vibration control

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Abstract

Traditional dynamic vibration absorbers (DVAs) consist of a mass-spring-damper system
and are an effective means of attenuating structural vibration over a narrow frequency
band. The effective bandwidth of the DVA can be increased by the addition of an
externally controlled force, generally applied between the reaction-mass and the primary
structure. Such devices are known as hybrid DVAs. This thesis presents a new hybrid
DVA configuration which utilizes two reaction-masses in parallel. On this proposed
hybrid dual-mass (DM) DVA, the control force is applied between the reaction-masses. It
is shown that in broadband control applications, the proposed DM-DVA requires less
control force to achieve the same primary attenuation as the traditional hybrid single-mass
(SM) DVA. The hybrid DM-DVA was compared to the hybrid SM-DVA with two tests.
A numerical simulation of the hybrid DVAs attenuating a single-degree-of-freedom
structure was performed. To achieve an equal amount of primary attenuation, the hybrid
SM-DVA required 65% higher root-mean-square (RMS) control effort than the hybrid
DV-DVA. The numerical model also demonstrated that the hybrid DM-DVA was less
sensitive to changes in the system as compared to the hybrid SM-DVA. Additionally, a
prototype hybrid DVA was built which could be configured as either the hybrid SM or
DM-DVA. The prototype hybrid DVA was used with the feedforward Filtered-X LMS
algorithm to control the vibration of a fixed-free beam. The hybrid SM and DM-DVAs
attenuated the primary response by a factor of 11.5 and 12.3, while requiring control
efforts of 4.9 and 2.7 V/N RMS, respectively. Thus, the hybrid DM-DVA required 45%
less control effort while yielding a higher attenuation ratio in this experiment. These
results demonstrate the superior performance of the proposed DM-DVA for broadband
control applications as compared to the traditional SM-DVA.